The objective of the proposed research is to study systematically the fetal liver from the nonhuman primate Macaca arctoides with respect to ultrastructure and drug metabolizing capacity, and compare it with that of human fetal liver. Drugs of abuse (barbiturates, morphine, methadone, meperidine, amphetamine derivatives) will be utilized as substrates. Studies will focus on the development of the oxidative drug metabolizing activity of the mixed function oxidase system of microsomal enzymes isolated from livers obtained from the fetal macaque. The biochemical findings will be correlated with ultrastructure. The aim is to evaluate the extent to which development of drug metabolism in the liver of the fetal macaque is comparable to that of the human and to relate our finding, inasmuch as possible, to clinical medicine. The long term research objective is to develop the fetal nonhuman primate into an animal model for the study of maternal-fetal drug interactions and their significance to the developing fetus. BIBLIOGRAPHIC REFERENCE: Dvorchik, B.H. and Stenger, V.G.: Drug biotransformation in microsomes from the fetal stumptailed macaque -Hepatic N- demethylation. Pharmacologist 17:303, 1975 (Abstract).